1. Field of the Invention
This invention relates to a system for fixing and guiding a bearing on a frame comprising two parallel uprights, a slot formed between them to receive the bearing and fixing members between the uprights and the bearing disposed straddle-fashion between the coplanar end faces of the respective uprights and of the bearing.
2. Description of Related Art
These bearings are used particularly for pivoting the cutting cylinders of rotary cutters in machines for making folding packing boxes from cardboard in strip form. These bearings are subjected to severe vibration conditions and abrupt dynamic force variations, so they have to be tightened and prestressed along three axes to guarantee optimal anti-vibration behavior.
Bearings of this kind should have only a single degree of freedom, the one defined by the slot for guiding the two parallel side surfaces of the bearing in engagement therewith, so that if the pressure exerted on the bearing exceeds a certain threshold in quite exceptional circumstances, the bearing can move only in that direction, thus enabling the spacing between the working cylinders to be increased.
It is therefore necessary to be able to move the upper cylinder away from the lower cylinder by a few tenths of a millimetre to release the shims, while guaranteeing replacement after exchange of the shims with an accuracy in accordance with the above-mentioned requirements and with minimum effort.
In the event of an accident, which is generally caused by cardboard jamming between the cutting cylinders, the bearings of the upper cylinder must be capable of moving along the slot in which they are guided in order to preserve the bearings and the cutting cylinders.
To this end, the bearing is immobilised in the slot by a pressure screw screwed into a yoke fixed to the top of the two uprights between which the bearing guide slot is formed. This yoke, which also serves to apply the uprights against the side surfaces of the bearing, is screwed to the ends of said uprights by calibrated screws which can elongate by creep or break beyond a specific pressure exerted on the bearing, said screws thus playing the same role as a fuse in an electrical circuit.
Fixing of the bearing of the lower cylinder is obtained by means of flat rectangular members disposed straddle-fashion along the two edges of the guide slot and screwed at its four corners to the bearing and to the adjacent upright. Such fixing gives no degree of freedom, so that it cannot be used for fixing the bearings of the upper cylinder if it is required to take advantage of the security mentioned above in the event of jamming. Also, such fixing does not enable the thickness of the shims to be changed.
Since cutting can be effected only for a spacing of micrometer precision between the cylinders and the spacing must be capable of adjustment periodically to allow for the wear of the cutting tools and specific operating conditions, the bearings of the two cylinders are separated by shims of variable thickness.
Consequently, the problem arising in fixing the bearings of the upper cylinder is complex and at present forms the subject matter of solutions using complex and complicated guide systems which give rise to problems associated with the dust and high pressures that they have to withstand.
The object of this invention is to at least partly obviate the above disadvantages.
To this end, the invention relates to a system for fixing and guiding a bearing on a frame.
The fixing member is a simple part to manufacture requiring no great precision except for its abutment surface which simply has to be planed to guarantee its contact with the end surfaces of the bearing and of the adjacent upright.
This fixing means enables the bearing to be given just a single degree of freedom in the direction of the slot. This degree of freedom serves to enable the bearing to be moved upwards a few tenths of a millimetre on the changing of the shims and this slight movement tends to move the uprights apart and hence reduce their pressure on the bearings, thus facilitating its release.
In the event of a greater displacement of the bearing, for example following a jam, the suspension strips initially tend to move the bearing uprights apart, and then they buckle with creep together with the fixing screws of the yoke connecting the top ends of the two uprights. This displacement is preferably limited by the spacing of the slots separating the fixing lugs.
The fixing member according to the invention can be screwed in place without any specific precaution after accurate positioning of the bearing in the slot and tightening of the yoke. Consequently, any displacement of the bearing within the limits of elastic deformation of the suspension strips enables the bearing to be extremely faithfully and easily replaced in position after the shims have been exchanged, since the elastically deformed suspension strips normally resume their initial shape, applying the bearing against the new shims.
Another advantage of the fixing system according to the invention is the maximum horizontal rigidity imparted to the bearing in comparison with any other known means. Thus if it is required to interpose needle elements between the slot and the bearing, the rigidity would be greatly reduced as a result.